Fix our handling of visibility in explicit template instantiations.

* Don't copy the visibility attribute during instantiations. We have to be able
  to distinguish

 struct HIDDEN foo {};
 template<class T>
 DEFAULT void bar() {}
 template DEFAULT void bar<foo>();

from

 struct HIDDEN foo {};
 template<class T>
 DEFAULT void bar() {}
 template void bar<foo>();

* If an instantiation has an attribute, it takes precedence over an attribute
  in the template.

* With instantiation attributes handled with the above logic, we can now
  select the minimum visibility when looking at template arguments.

llvm-svn: 156821

clang/include/clang/Basic/Attr.td

@@ -93,6 +93,9 @@ class Attr {
   list<string> Namespaces = [];
   // Set to true for attributes with arguments which require delayed parsing. 
   bit LateParsed = 0;  
+  // Set to false to prevent an attribute from being propagated from a template
+  // to the instantiation.
+  bit Clone = 1;
   // Set to true for attributes which must be instantiated within templates
   bit TemplateDependent = 0;
   // Set to true for attributes that have a corresponding AST node.
@@ -660,6 +663,7 @@ def VecTypeHint : Attr {
 }
 
 def Visibility : InheritableAttr {
+  let Clone = 0;
   let Spellings = ["visibility"];
   let Args = [EnumArgument<"Visibility", "VisibilityType",
                            ["default", "hidden", "internal", "protected"],

clang/lib/AST/Decl.cpp

@@ -158,14 +158,12 @@ getLVForTemplateArgumentList(const TemplateArgumentList &TArgs,
   return getLVForTemplateArgumentList(TArgs.data(), TArgs.size(), OnlyTemplate);
 }
 
-static bool shouldConsiderTemplateLV(const FunctionDecl *fn,
-                               const FunctionTemplateSpecializationInfo *spec) {
-  return !(spec->isExplicitSpecialization() &&
-           fn->hasAttr<VisibilityAttr>());
+static bool shouldConsiderTemplateLV(const FunctionDecl *fn) {
+  return !fn->hasAttr<VisibilityAttr>();
 }
 
 static bool shouldConsiderTemplateLV(const ClassTemplateSpecializationDecl *d) {
-  return !(d->isExplicitSpecialization() && d->hasAttr<VisibilityAttr>());
+  return !d->hasAttr<VisibilityAttr>();
 }
 
 static LinkageInfo getLVForNamespaceScopeDecl(const NamedDecl *D,
@@ -376,7 +374,7 @@ static LinkageInfo getLVForNamespaceScopeDecl(const NamedDecl *D,
     // this is an explicit specialization with a visibility attribute.
     if (FunctionTemplateSpecializationInfo *specInfo
                                = Function->getTemplateSpecializationInfo()) {
-      if (shouldConsiderTemplateLV(Function, specInfo)) {
+      if (shouldConsiderTemplateLV(Function)) {
         LV.merge(getLVForDecl(specInfo->getTemplate(),
                               true));
         const TemplateArgumentList &templateArgs = *specInfo->TemplateArguments;
@@ -407,8 +405,8 @@ static LinkageInfo getLVForNamespaceScopeDecl(const NamedDecl *D,
 
         // The arguments at which the template was instantiated.
         const TemplateArgumentList &TemplateArgs = spec->getTemplateArgs();
-        LV.merge(getLVForTemplateArgumentList(TemplateArgs,
-                                              OnlyTemplate));
+        LV.mergeWithMin(getLVForTemplateArgumentList(TemplateArgs,
+                                                     OnlyTemplate));
       }
     }
 
@@ -527,7 +525,7 @@ static LinkageInfo getLVForClassMember(const NamedDecl *D, bool OnlyTemplate) {
     // the template parameters and arguments.
     if (FunctionTemplateSpecializationInfo *spec
            = MD->getTemplateSpecializationInfo()) {
-      if (shouldConsiderTemplateLV(MD, spec)) {
+      if (shouldConsiderTemplateLV(MD)) {
         LV.mergeWithMin(getLVForTemplateArgumentList(*spec->TemplateArguments,
                                                      OnlyTemplate));
         if (!OnlyTemplate)

clang/lib/Sema/SemaTemplateInstantiateDecl.cpp

@@ -102,7 +102,8 @@ void Sema::InstantiateAttrs(const MultiLevelTemplateArgumentList &TemplateArgs,
     } else {
       Attr *NewAttr = sema::instantiateTemplateAttribute(TmplAttr, Context,
                                                          *this, TemplateArgs);
-      New->addAttr(NewAttr);
+      if (NewAttr)
+        New->addAttr(NewAttr);
     }
   }
 }

clang/test/CodeGenCXX/visibility.cpp

@@ -712,3 +712,55 @@ namespace test36 {
   // CHECK: define weak_odr hidden void @_ZN6test363fooINS_2S1ENS_2S2EE3barEv
   // CHECK-HIDDEN: define weak_odr hidden void @_ZN6test363fooINS_2S1ENS_2S2EE3barEv
 }
+
+namespace test37 {
+  struct HIDDEN foo {
+  };
+  template<class T>
+  DEFAULT void bar() {}
+  template DEFAULT void bar<foo>();
+  // CHECK: define weak_odr void @_ZN6test373barINS_3fooEEEvv
+  // CHECK-HIDDEN: define weak_odr void @_ZN6test373barINS_3fooEEEvv
+}
+
+namespace test38 {
+  template<typename T>
+  class DEFAULT foo {
+    void bar() {}
+  };
+  struct HIDDEN zed {
+  };
+  template class foo<zed>;
+  // CHECK: define weak_odr hidden void @_ZN6test383fooINS_3zedEE3barEv
+  // CHECK-HIDDEN: define weak_odr hidden void @_ZN6test383fooINS_3zedEE3barEv
+}
+
+namespace test39 {
+  class DEFAULT default_t;
+  class HIDDEN hidden_t;
+  template <class T> class A {
+    template <class U> class B {
+      HIDDEN void hidden() {}
+      void noattr() {}
+      template <class V> void temp() {}
+    };
+  };
+  template class DEFAULT A<hidden_t>;
+  template class DEFAULT A<hidden_t>::B<hidden_t>;
+  template void A<hidden_t>::B<hidden_t>::temp<default_t>();
+  template void A<hidden_t>::B<hidden_t>::temp<hidden_t>();
+
+  // CHECK: define weak_odr hidden void @_ZN6test391AINS_8hidden_tEE1BIS1_E6hiddenEv
+  // CHECK: define weak_odr void @_ZN6test391AINS_8hidden_tEE1BIS1_E6noattrEv
+  // CHECK: define weak_odr void @_ZN6test391AINS_8hidden_tEE1BIS1_E4tempINS_9default_tEEEvv
+
+  // GCC produces a default for this one. Why?
+  // CHECK: define weak_odr hidden void @_ZN6test391AINS_8hidden_tEE1BIS1_E4tempIS1_EEvv
+
+  // CHECK-HIDDEN: define weak_odr hidden void @_ZN6test391AINS_8hidden_tEE1BIS1_E6hiddenEv
+  // CHECK-HIDDEN: define weak_odr void @_ZN6test391AINS_8hidden_tEE1BIS1_E6noattrEv
+  // CHECK-HIDDEN: define weak_odr void @_ZN6test391AINS_8hidden_tEE1BIS1_E4tempINS_9default_tEEEvv
+
+  // GCC produces a default for this one. Why?
+  // CHECK-HIDDEN: define weak_odr hidden void @_ZN6test391AINS_8hidden_tEE1BIS1_E4tempIS1_EEvv
+}

clang/utils/TableGen/ClangAttrEmitter.cpp

@@ -1004,6 +1004,14 @@ void ClangAttrTemplateInstantiateEmitter::run(raw_ostream &OS) {
       continue;
 
     OS << "    case attr::" << R.getName() << ": {\n";
+    bool ShouldClone = R.getValueAsBit("Clone");
+
+    if (!ShouldClone) {
+      OS << "      return NULL;\n";
+      OS << "    }\n";
+      continue;
+    }
+
     OS << "      const " << R.getName() << "Attr *A = cast<"
        << R.getName() << "Attr>(At);\n";
     bool TDependent = R.getValueAsBit("TemplateDependent");